In collaboration with J. Moore at the University of Illinois, we have used high resolution X-Ray diffraction to study the structure of a liquid crystalline conjugated phenylacetylene macrocycle (PAM) [1]. Columnar mesophases based on these rigid ring-shaped molecules are of interest because of their potential self-organization into supramolecular channels. The PAM studied forms a columnar liquid crystal. Our diffraction studies showed that the structure is not hexagonal, as previously believed. Rather, the structure is monoclinic, and can be derived from a hexagonal columnar structure via a distortion of the hexagonal mesh followed by a period doubling along one axis. We also doped PAM with Ag ions (three different weight percentages of AgOTf) and studied the structure of the doped compounds. Metal doping of PAM is of great interest because of the possibility of the anisotropic conductivity. We founds that the doped compounds had the same lattice structure as the undoped compounds; a detailed structural analysis is presently underway. [1] J. Zhang and J. Moore J. Am. Chem. Soc. 116: 2655, 1994 and references therein.